Effect of Adlayer Structure on the Host−Guest Recognition between Calcium and Crown-Ether-Substituted Phthalocyanine Arrays on Au Single-Crystal Surfaces

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Abstract
Adlayers of 15-crown-5-ether-substituted cobalt(II) phthalocyanine (CoCRPc) were prepared by immersion of either Au(111) or Au(100) substrate into benzene−ethanol (9:1 v/v) mixed solutions containing CoCRPc. In situ STM imaging was carried out after transferring the CoCRPc-modified Au crystals into aqueous HClO4 solution. The packing arrangement of the CoCRPc array on Au(111) was determined to be p(8 × 4√3R − 30°), and the internal structure was clearly observed by high-resolution STM. Two adlayer structures of CoCRPc, (8 × 9) and (4√5 × 4√5)R26.7°, were found on the Au(100)−(1 × 1) terrace. In the presence of 1 mM Ca2+, two Ca2+ ions were trapped in two diagonally located 15-crown-5-ether moieties of each CoCRPc molecule on Au(111), whereas encapsulation of Ca2+ ions was not seen in the CoCRPc arrays on the Au(100)−(1 × 1) surface. The present study demonstrates that the relationship between crown moieties of CRPc and the underlying Au lattice is important in the trapping of Ca2+ ions in crown rings.

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